The present invention relates to an aluminum alloy for high pressure die-casting, and more particularly, to the alloy for providing parts and components of a vehicle.
Conventionally, ADC10 alloy or ADC12 alloy are used as a high pressure die-casting material, in case that parts and components of a vehicle are produced by high pressure die-casting in light of mass-production and productivity. These alloys are Alxe2x80x94Sixe2x80x94Cu alloy and are available for a product having a complicated configuration such as a cover member and a case, because these materials have relatively high strength and provide sufficient castability.
In view of a recent trend of environmental protection and recycling, a demand of producing a frame and a body of a vehicle with aluminum alloy by high pressure die-casting is bringing into attention because the aluminum alloy is light in weight and is capable of recycling. However, ADC10 alloy and ADC12 alloy provide inferior ductility and toughness, and therefore are not available as a material of the frame and body of the vehicle.
Laid open Japanese Patent Application Publication Nos. Hei 1-247549 and Hei 11-193434 disclose a composite alloy in which Mn and Ni are added into Alxe2x80x94Mg multiple elements alloy. This alloy is available for high pressure die-casting. However, such composite alloy is not appropriate as a material of the frame and body of the vehicle, because elongation is low such as about 10%. Further, a material exhibiting high elongation available for the frame and body generally provides low mechanical strength at high temperature. Therefore, a cast product made from the highly elongatable material may be deformed when separating from a metal mold of a high pressure die-casting apparatus.
In case of a low pressure die-casting other than the high pressure die-casting, AC 4CH alloy providing relatively high elongation is used and a cast product is subjected to T6 treatment (defined by JIS H 0001), or AC7A alloy is used. These materials provide a sufficient strength and elongation required in the frame and the body. However, such materials are not available for producing thin and elongated parts such as a pillar of the vehicle body. Further, the cast product must be subjected to heat treatment in the employment of AC 4CH alloy, which is costly. Moreover, thermal seizure to the metal mold may often occur in the employment of AC7A alloy, which is detrimental to the cast product.
It is an object of the present invention to overcome the above-described problems and to provide an aluminum alloy for a high pressure die-casting available for producing a frame and body of a vehicle while meeting with the requirements of mechanical strength (not less than 250 MPa) and elongation (not less than 15%), yet reducing defects of casting.
This and other objects of the present invention will be attained by providing an aluminum alloy for high pressure die-casting containing from 3.6 to 5.5 mass % of Mg, from 0.6 to 1.2 mass % of Mn, from 0.2 to less than 0.5 mass % of Ni, and the balance aluminum and inevitable impurities.
With the composition, resultant cast product can pro-vide strength of not less than 320MPa and elongation of not less than 20%, those meeting with the requirements in the frame and body of a vehicle. Further, insufficient casting can be reduced.
Preferably, the aluminum alloy further contains from 0.001 to 0.010 mass % of Be. This arrangement can prevent Mg from being oxidized. Therefore, reduction in density of Mg can be avoided.
Further preferably, the aluminum alloy further includes at least one of from 0.01 to 0.3 mass % of Ti and from 0.001 to 0.05 mass % of B. With this arrangement, crystal grain refinement can be promoted to enhance castability.